Instrument dial illumination



May 28, 1940. l.. F. CARTER 2,202,142 INSTRUMENT DIAL' ILLUMINATION A Filed March 27, 1937 Y INVENTOR ze F.' Garer Patented May 28,

Leslie F. Carter, Leonia, N. J., assi'gnor to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation 'of New York Application March 21, 1937, serial No. 133,313

imams.A (ci. 24o- 2.1)

This invention relates to illuminating means for indicators such as employed on the dashboards of automobiles or the instrument panels of aircraft. In both cases a system of indirect l illumination is'desirable, wherein a minimum amount of light is reflected into the eyes of the observer, but` the indications are'rendered distinctly visible from the drivers or pilots seat.

My invention is shown as applied to a form of l0 aircraft instrument known as an artificial or gyro horizon, but it is obvious 'that it may be applied to other types of instruments. Itv is especially designed, however, for-instruments op- Y erated by air, in which the casing is sealed, so ll that removal of the lamp will not disturb the vacuum within the casing. Referring to the drawing,'showing one form my invention may assume:

Fig. 1 is a front elevation, partly in section, of 20 an artificial horizon with my invention applied thereto. .I

Fig. 2 is a vertical section, onvan enlarged scale, through the front upper portion of the casing.

Fig, 3 is an enlarged portion of Fig. 1, partly in 9,5A section, the left hand part being taken on section line X-X in Fig. 4 and the right hand part on section line Y-Y in Fig.'4. Fig. 4 is a sectional view of the upper portion of Fig. 2, with the lamp and wires removed. 3g Fig. 5 isa'section on line 5 5. of Fig. 1.

As stated above, most of the aircraft instruments` are air driven, the casing l being sealed and having air continuously withdrawn therefrom through pipe connection 2. The front plate 5 of 35 the casing is shown as having a front window ,3 which is held in place by a snap ring, 4 which tightly lits in annular rib 5 projecting from. plate 5. Preferably said window is spaced from the inner ange 6 of plate 5. 'Ihis may be accomplished by making the window with. an inwardly extending circumferential Vannulus or rim 'l which spaces the window from said'ange, as

frontwindow, as was proposed inl my prior application for Illuminator for indicator dials,v Serial No. 76,984, led April 29, 1936, now Patent No.

12,131,471 f September 27, 1.938. This has the l `whatever transparent material 'is used for the advantage over the prior application of not showing up imperfectionsin or nger marks on the glass face, and 'of transmitting a greater portion of the light `by not having toftransmit` through, so much of the longitudinal section of glassor window. It also utilizes the under surface of thewindow as a reecting surface as well as the upper surface, so that more light is reiiected onto i the'movableindicators 20 and 2i. If desired, the

portion of the rim. immediately under the light may be painted orground to reduce the light entering at that point, as indicated at |'.V

The lamp is shown as provided with a screw base i0 so that it may be screwed into the threaded thimble orsocket ii which is connected to one of the wires i2.. 'Ihe other wire I3 is connected to a small ring i4 insulated from.- thimble Il and contacting with the shank I of the lamp holder in the well known manner. The main casing i is provided with a cut-out portion at its top, into which is fastened the lamp holding and reecting member I B, which carries the lampl holder and is preferably of insulating material. 'I'his member I has an upper inner reflecting surface curved in the rim 'i soasv to direct light rays through the shown in Fig. 2. Graduations 22 may be provided on the thin-ring 8 behind said window, to which is attached a fixed indicator 8' in the form of an airplane. rI 'he movable indicators shown as horizon bar 20 and index 2| lie behind ring 8, but close enough thereto to be illuminated from the same lamp that illuminates the gradua- 50 tions 22.

The lamp 9` is placed opposite the transparent rim l, i. e., with its filament below the under surface of window 3, so that the major portion of the light will shine through said rim instead of transversely through the entire thickness of thereflects the light onto the instrument dial. The

rim through a substantial arc and not all at one point. All of said surfaces are painted with yreflecting paint so that the light is directed downwardly through rim I and underneath the front glass 3, so that the under surface of the glass to illuminate more than one-instrument diaLif desired, as indicated in my aforesaid applica-` tion.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could made without departing from the .scope theeoi', it is intendedthat all matter contained in`the above description orshown in the accompanying drawing shall be interpreted not in a limiting sense..

at 25. This has the advantage of refracting the Zig-ht rays from the lamp inwardly toward thegraduations 22 and index 2I,givin'g^emcient llumination especially around the periphery o f the dial.

Having described my invention, what rciaim' and desire to secure by Letters Patent is:

1. In an indicating instrument having a front plate with anbpening therein through which the indicator behind said plate is visible, afLat-window in said opening spaced from the front -plate by a circular rim extension or ring, asmall lamp positioned adjacent the space between said winsaid lamp holder.

.tiallyy uniform illuminationl oi the dial is secured.

2. An illuminating device for instrument panels of vehicles, comprising a casing having a transparent window consisting of a at pane and a circulan :dat rim extension thereunder, indications behind said window within said casing, alamp holder of insulating material to one side of said window and securedto the exterior of said casing,v .v 1- -v p an velectric light bulb in said' holder withits yiilti- In Fig. 5, for instance, the inner` periphery;of?? the iiange or rim 'l of the glass window is shown as perpendicular to the face, but irl-Fig. 2ithis inner surface is shown as beveled outwardly, as

mentbehind the inner face of said window oppoysite said extension, but in front of said indications, and a purality of reectors of different cux'vaturesl behind said lamp to direct llight through a substantial arc of said rim.

' 3. -In an illuminating device forinstruments of vehicles, a casing, a-dial in lsaid casing, a'transrent ,window in said casing consisting of a pane aving substantially plane and parallel surfaces and anannular transparent extension toward said dial, a lamp and lamp holder vtherefor adjacent said casing and the rimof said extension, Y

part of. said rim nearest said lamp.lwhereby excessive illumination of any part of said dial is prevented.

4. An illuminating device as`claimed in claim 3, in which said reiiectors are formed as part of LESHEF. CARTER.

.a plurality. of reflectors-of diierent curvatures behind said lamp,` and an opaque'mask covering 

